Intresting links on QSL card :

A link on who invented QSL card

http://www.qsl.at/english/en_qslstory.html

Old QSL cards

http://geocities.com/w8jyz/

K8CX QSL card gallery

http://hamgallery.com/qsl/

QSL's from ARRL Deleted DXCC Entities

http://hamgallery.com/qsl/deleted/

QSLing Those Radio Memories

http://www.arrl.org/news/features/2008/11/28/10471/

Source : Thanks to my friend VU2WSM for passing these QSP.